Parsing Json url using async

2020-05-06 10:59发布

站内文章 / Android
67 0 0

问题:

I get exceptions when running this code. I want to parse the url which is an array of json objects:

package com.example.compsci_734t;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;

public class UoaCompsciActivity extends Activity {

    private static String url = " http://redsox.tcs.auckland.ac.nz/734A/CSService.svc/courses";
    //URL requestUrl = new URL(url);
    JSONArray courses = null;
    private static final String TAG_COURSES = "Courses";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_uoa_compsci);
        new MyTask().execute();
    }


    private class MyTask extends AsyncTask<URL, Void, JSONObject> {

        @Override
        protected JSONObject doInBackground(URL... urls) {
            loadJSON(url);
            return null;
        }

        protected void onPostExecute(JSONObject json) {

            try {
                courses = json.getJSONArray(TAG_COURSES);

                // looping through all courses
                for (int i = 0; i < courses.length(); i++) {
                    JSONObject c = courses.getJSONObject(i);

                    // Storing each json item in variable
                    String course_id = c.getString("courseField:");
                    String course_name = c.getString("titleField:");
                    String course_semester = c.getString("semesterField:");



                    Log.v("--", "Course: \n" + " " + course_id + " " + course_name
                            + " " + course_semester);
                }

        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
    }


    public JSONObject loadJSON(String url) {
        // Creating JSON Parser instance
        JSONParser jParser = new JSONParser();

        // getting JSON string from URL
         JSONObject json = jParser.getJSONFromUrl(url);

        return json;
    }

}

Also here is my logcat: 

05-13 20:29:05.118: I/dalvikvm(770): threadid=3: reacting to signal 3
05-13 20:29:05.128: I/dalvikvm(770): Wrote stack traces to '/data/anr/traces.txt'
05-13 20:29:05.418: D/gralloc_goldfish(770): Emulator without GPU emulation detected.
05-13 20:31:46.128: I/dalvikvm(842): threadid=3: reacting to signal 3
05-13 20:31:46.218: I/dalvikvm(842): Wrote stack traces to '/data/anr/traces.txt'
05-13 20:31:46.408: D/gralloc_goldfish(842): Emulator without GPU emulation detected.
05-13 22:06:17.298: I/dalvikvm(918): threadid=3: reacting to signal 3
05-13 22:06:17.389: I/dalvikvm(918): Wrote stack traces to '/data/anr/traces.txt'
05-13 22:06:17.549: D/gralloc_goldfish(918): Emulator without GPU emulation detected.
05-13 22:06:17.829: W/dalvikvm(918): threadid=11: thread exiting with uncaught exception (group=0x409c01f8)
05-13 22:06:17.839: E/AndroidRuntime(918): FATAL EXCEPTION: AsyncTask #1
05-13 22:06:17.839: E/AndroidRuntime(918): java.lang.RuntimeException: An error occured while executing doInBackground()
05-13 22:06:17.839: E/AndroidRuntime(918):  at android.os.AsyncTask$3.done(AsyncTask.java:278)
05-13 22:06:17.839: E/AndroidRuntime(918):  at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
05-13 22:06:17.839: E/AndroidRuntime(918):  at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
05-13 22:06:17.839: E/AndroidRuntime(918):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
05-13 22:06:17.839: E/AndroidRuntime(918):  at java.util.concurrent.FutureTask.run(FutureTask.java:137)
05-13 22:06:17.839: E/AndroidRuntime(918):  at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208)
05-13 22:06:17.839: E/AndroidRuntime(918):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
05-13 22:06:17.839: E/AndroidRuntime(918):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
05-13 22:06:17.839: E/AndroidRuntime(918):  at java.lang.Thread.run(Thread.java:856)
05-13 22:06:17.839: E/AndroidRuntime(918): Caused by: java.lang.IllegalArgumentException: Illegal character in scheme at index 0:  http://redsox.tcs.auckland.ac.nz/734A/CSService.svc/courses
05-13 22:06:17.839: E/AndroidRuntime(918):  at java.net.URI.create(URI.java:727)
05-13 22:06:17.839: E/AndroidRuntime(918):  at org.apache.http.client.methods.HttpPost.<init>(HttpPost.java:79)
05-13 22:06:17.839: E/AndroidRuntime(918):  at com.example.compsci_734t.JSONParser.getJSONFromUrl(JSONParser.java:36)
05-13 22:06:17.839: E/AndroidRuntime(918):  at com.example.compsci_734t.UoaCompsciActivity.loadJSON(UoaCompsciActivity.java:78)
05-13 22:06:17.839: E/AndroidRuntime(918):  at com.example.compsci_734t.UoaCompsciActivity$MyTask.doInBackground(UoaCompsciActivity.java:42)
05-13 22:06:17.839: E/AndroidRuntime(918):  at com.example.compsci_734t.UoaCompsciActivity$MyTask.doInBackground(UoaCompsciActivity.java:1)
05-13 22:06:17.839: E/AndroidRuntime(918):  at android.os.AsyncTask$2.call(AsyncTask.java:264)
05-13 22:06:17.839: E/AndroidRuntime(918):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
05-13 22:06:17.839: E/AndroidRuntime(918):  ... 5 more

updated logcat:

05-13 22:15:01.438: I/dalvikvm(968): threadid=3: reacting to signal 3
05-13 22:15:01.598: I/dalvikvm(968): Wrote stack traces to '/data/anr/traces.txt'
05-13 22:15:01.718: D/gralloc_goldfish(968): Emulator without GPU emulation detected.
05-13 22:15:02.288: E/JSON Parser(968): Error parsing data org.json.JSONException: Value <?xml of type java.lang.String cannot be converted to JSONObject
05-13 22:15:02.288: D/AndroidRuntime(968): Shutting down VM
05-13 22:15:02.288: W/dalvikvm(968): threadid=1: thread exiting with uncaught exception (group=0x409c01f8)
05-13 22:15:02.298: E/AndroidRuntime(968): FATAL EXCEPTION: main
05-13 22:15:02.298: E/AndroidRuntime(968): java.lang.NullPointerException
05-13 22:15:02.298: E/AndroidRuntime(968):  at com.example.compsci_734t.UoaCompsciActivity$MyTask.onPostExecute(UoaCompsciActivity.java:49)
05-13 22:15:02.298: E/AndroidRuntime(968):  at com.example.compsci_734t.UoaCompsciActivity$MyTask.onPostExecute(UoaCompsciActivity.java:1)
05-13 22:15:02.298: E/AndroidRuntime(968):  at android.os.AsyncTask.finish(AsyncTask.java:602)
05-13 22:15:02.298: E/AndroidRuntime(968):  at android.os.AsyncTask.access$600(AsyncTask.java:156)
05-13 22:15:02.298: E/AndroidRuntime(968):  at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:615)
05-13 22:15:02.298: E/AndroidRuntime(968):  at android.os.Handler.dispatchMessage(Handler.java:99)
05-13 22:15:02.298: E/AndroidRuntime(968):  at android.os.Looper.loop(Looper.java:137)
05-13 22:15:02.298: E/AndroidRuntime(968):  at android.app.ActivityThread.main(ActivityThread.java:4424)
05-13 22:15:02.298: E/AndroidRuntime(968):  at java.lang.reflect.Method.invokeNative(Native Method)
05-13 22:15:02.298: E/AndroidRuntime(968):  at java.lang.reflect.Method.invoke(Method.java:511)
05-13 22:15:02.298: E/AndroidRuntime(968):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
05-13 22:15:02.298: E/AndroidRuntime(968):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
05-13 22:15:02.298: E/AndroidRuntime(968):  at dalvik.system.NativeStart.main(Native Method)
05-13 22:15:02.889: I/dalvikvm(968): threadid=3: reacting to signal 3
05-13 22:15:02.919: I/dalvikvm(968): Wrote stack traces to '/data/anr/traces.txt'

full logcat: 05-13 22:15:01.438: I/dalvikvm(968): threadid=3: reacting to signal 3 05-13 22:15:01.598: I/dalvikvm(968): Wrote stack traces to '/data/anr/traces.txt' 05-13 22:15:01.718: D/gralloc_goldfish(968): Emulator without GPU emulation detected. 05-13 22:15:02.288: E/JSON Parser(968): Error parsing data org.json.JSONException: Value 

回答1:

The error is explanatory itself:

java.lang.IllegalArgumentException: Illegal character in scheme at index 0

You need to remove the beginning space character in your URL:

private static String url = "http://redsox.tcs.auckland.ac.nz/734A/CSService.svc/courses";

Update:

After you've updated your question, now the problem seems in this line:

courses = json.getJSONArray(TAG_COURSES);

because you haven't initialized or set the value of courses that's why its giving NullPointerException error.



回答2:

It is not related to JSON parsing. 

  private static String url = " http://redsox.tcs.auckland.ac.nz/734A/CSService.svc/courses";

you have to remove the initial space from the url string



回答3:

Hi its due to some problem in the webservice maybe due toh the encoding problem its not your or android's problem. Just as you get response in that string just replace the character you get with "".

response= response.replace("","");

and then do your parsing after this. It worked for me. I hope it works for you also.....



回答4:

I have solved it. Thanks for all your help. I also converted the parsed stuff into a list view. This is my working code:

package com.example.compsci_734t;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.net.URL;
import java.util.ArrayList;
import java.util.zip.GZIPInputStream;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;





import android.app.Activity;
import android.app.ListActivity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.ListView;



public class People extends Activity{

        ArrayList<String> items = new ArrayList<String>();
        static InputStream is = null;
        //private static String url = "";
        //private static String url = "http:...";
        private static String url = "http....";
        //URL requestUrl = new URL(url);
        JSONArray people = null;
        private static final String TAG_COURSES = "Courses";
        static JSONObject jObj = null;
        static String json = "";

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.people);
            new MyTasks().execute();
        }


        private class MyTasks extends AsyncTask<URL, Void, JSONObject> {

            @Override
            protected JSONObject doInBackground(URL... urls) {
               // return loadJSON(url);
                try {
                    // defaultHttpClient
                    DefaultHttpClient httpClient = new DefaultHttpClient();
                    //HttpPost httpPost = new HttpPost(url);
                    HttpGet httpGet = new HttpGet(url);
                    HttpResponse httpResponse = httpClient.execute(httpGet);

                    HttpEntity httpEntity = httpResponse.getEntity();
                    is = httpEntity.getContent();

                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                } catch (ClientProtocolException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
              try {
                /*BufferedReader reader = new BufferedReader(new InputStreamReader(
                        is, "UTF-8"), 8);*/
                InputStream inputStream = is;
                GZIPInputStream input = new GZIPInputStream(inputStream);
                InputStreamReader reader = new InputStreamReader(input);
                BufferedReader in = new BufferedReader(reader);
                StringBuilder sb = new StringBuilder();
                String line = null;
                while ((line = in.readLine()) != null) {
                    sb.append(line);
                   //System.out.println(line);
                }
                is.close();
                json = sb.toString();
            } catch (Exception e) {
                Log.e("Buffer Error", "Error converting result " + e.toString());
            }

            // try parse the string to a JSON object

            try {

                JSONArray people = new JSONArray(json);
                //JSONArray people = new JSONArray(json);

                for (int i = 0; i < people.length(); i++) {
                    //System.out.println(courses.getJSONObject(i).toString());
                    JSONObject p = people.getJSONObject(i);

                    // Storing each json item in variable
                    String person_id = p.getString("someString1");


                    items.add(person_id);

                    /*Log.v("--", "People: \n" + "\n UPI: " + person_id);*/
                }


                //jObj = new JSONObject(json);
            } catch (JSONException e) {
                Log.e("JSON Parser", "Error parsing data " + e.toString());
            } 

            // return JSON String
            return jObj;
            }

            protected void onPostExecute(JSONObject json) {
                ListView myListView = (ListView)findViewById(R.id.peopleList);
                myListView.setAdapter(new ArrayAdapter(getApplicationContext(), android.R.layout.simple_list_item_1, items));
        }
        }


回答5:

  1. I have solved it.....tRy it really work
package com.example.json_test;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.net.URL;
import java.util.ArrayList;
import java.util.zip.GZIPInputStream;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class MainActivity extends Activity
{

        ArrayList<String> items = new ArrayList<String>();
        static InputStream is = null;
        private static String url = "http://redsox.tcs.auckland.ac.nz/734A/CSService.svc/courses";
        JSONArray people = null;
        private static final String TAG_COURSES = "codeField";
        private static final String TAG_SEMESTER="semesterField";
        static JSONObject jObj = null;
        static String json = "";

        @Override
        public void onCreate(Bundle savedInstanceState) 
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            new MyTasks().execute();
        }


        private class MyTasks extends AsyncTask<URL, Void, JSONObject> 
        {

            @Override
            protected JSONObject doInBackground(URL... urls) 
            {
                try 
                {
                    DefaultHttpClient httpClient = new DefaultHttpClient();
                    HttpGet httpGet = new HttpGet(url);
                    HttpResponse httpResponse = httpClient.execute(httpGet);

                    HttpEntity httpEntity = httpResponse.getEntity();
                    is = httpEntity.getContent();

                } 
                catch (UnsupportedEncodingException e) 
                {
                    e.printStackTrace();
                } 
                catch (ClientProtocolException e) 
                {
                    e.printStackTrace();
                } catch (IOException e) 
                {
                    e.printStackTrace();
                }
              try 
              {
                InputStream inputStream = is;
                GZIPInputStream input = new GZIPInputStream(inputStream);
                InputStreamReader reader = new InputStreamReader(input);
                BufferedReader in = new BufferedReader(reader);
                StringBuilder sb = new StringBuilder();
                String line = null;

                while ((line = in.readLine()) != null) 
                {
                    sb.append(line);
                }
                is.close();
                json = sb.toString();
            } catch (Exception e) 
            {
                Log.e("Buffer Error", "Error converting result " + e.toString());
            }
            try 
            {

                JSONArray people = new JSONArray(json);

                for (int i = 0; i < people.length(); i++) 
                {
                    JSONObject p = people.getJSONObject(i);
                    String Courses = p.getString(TAG_COURSES);
                    String semester=p.getString(TAG_SEMESTER);

                    items.add(Courses);
                    items.add(semester);
                }

            } catch (JSONException e) 
            {
                Log.e("JSON Parser", "Error parsing data " + e.toString());
            } 
            return jObj;
            }

            @SuppressWarnings({ "unchecked", "rawtypes" })
            protected void onPostExecute(JSONObject json) 
            {
                ListView myListView = (ListView)findViewById(R.id.peopleList);
                myListView.setAdapter(new ArrayAdapter(getApplicationContext(), android.R.layout.simple_list_item_1, items));
        }
        }
}


标签： android json parsing android-asynctask
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